This application is a continuation of international application number PCT/EP99/03432 filed on May 19, 1999.
The present disclosure relates to the subject matter disclosed in International Application No. PCT/EP99/03432 of May 19, 1999, the entire specification of which is incorporated herein by reference. The invention relates to a lithography exposure device for producing structures extending in a surface area in a light-sensitive layer with a mounting device for the light-sensitive layer, with an exposure unit comprising at least one laser radiation source, an optical focusing means for the laser radiation associated with the laser radiation source and a screen associated with the optical focusing means and comprising a screen aperture which is elongated in a longitudinal direction and with which a radiation field can be generated in the light-sensitive layer which has in a lateral direction extending transversely to the longitudinal direction of the screen aperture an effective lateral extension which is in the order of magnitude of the wavelength of the laser radiation or smaller, with a movement unit for generating a relative movement between the optical focusing means and the mounting device and with a control for controlling the intensity and position of the radiation field relative to the light-sensitive layer in such a manner that a plurality of conversion areas can be generated in the light-sensitive layer by means of a large number of successive exposure steps and in these conversion areas the material of the light-sensitive layer is converted from an initial state into a converted end state and they together result in the structures.
A lithography exposure device of this type is known from WO 98/00760. This lithography exposure device is, however, provided only for representing structures, the extension of which is greater than that of the radiation field.
The object underlying the invention is to create a lithography exposure device, with which it is possible to produce, without masks, structures which have in at least one direction an extension which is smaller than that of one of the radiation fields used.
The object of the present invention is, in particular, to create a lithography exposure device, with which structures can be produced in the range of less than 200 nanometers extension.
This object is accomplished in accordance with the invention, by a lithography exposure device of the type described at the outset, in that with at least some of the exposure steps the control generates radiation fields with a distribution of energy which makes the action of at least two radiation fields on the same conversion area necessary in order to transfer the material of the light-sensitive layer in this area into the converted end state.
The core of the inventive solution is thus to be seen in the fact that the intensity and the distribution of the intensity of the radiation fields used is adjusted such that the effect of one radiation field in the area of action of the light-sensitive layer does not lead to a transfer of the material from the initial state into the converted end state but rather merely to a partial conversion which does not yet have the desired state. Only the action of at least a second radiation field on the same conversion area creates the possibility that in the area, in which the two radiation fields overlap, the possibility exits of a complete conversion of the material of the light-sensitive layer into the converted state insofar as the distributions of the intensity are such that the sum of the intensities in the conversion area is sufficiently large to exceed the threshold intensity for the conversion of the light-sensitive material from the initial state into the converted state.
It is thus possible, due to the use and the action of two radiation fields and the fact that the effects of the intensities have to be added together in order to exceed the threshold for the conversion of the material of the light-sensitive layer, to produce at least sections of structures, in which the extension of the sections in one direction is at the most of the same size if not smaller than the extension of one of the radiation fields in the respective direction.
In principle, it is possible to give each radiation field such a distribution of intensity that even with congruent superposition of at least two radiation fields the threshold for the conversion of the material of the light-sensitive layer from the initial state into the converted state is exceeded only in one section of the radiation fields and so the congruent superposition of two radiation fields already leads, in the long run, to a conversion area which has in at least one direction an extension which is smaller than that of the two utilized radiation fields themselves.
One particularly favorable solution does, however, provide for the two radiation fields acting on the same conversion area to be arranged so as not to be congruent but rather only partially overlapping so that a conversion area corresponding at the most to the overlapping area can already be generated due to the partial overlapping of the radiation fields and this conversion area has in the direction of the partial overlapping an extension which is smaller than that of one of the radiation fields themselves.
With the overlapping arrangement of two radiation fields it is possible to arrange the radiation fields in a parallel alignment in relation to one another, i.e. with longitudinal directions extending parallel to one another, namely such that these partially overlap.
One particularly advantageous solution provides for a first radiation field aligned in a first direction to be arranged so as to overlap with a second radiation field extending in a second direction at an angle or transversely to the first for generating a conversion area so that a complete overlapping is already excluded from the outset due to the radiation fields extending at an angle or transversely to one another and only a partial overlapping is possible, and thus the conversion area can have at the most an extension which corresponds to the overlapping area of the two radiation fields.
In this respect, it is particularly advantageous when the second radiation field extends essentially at right angles relative to the first radiation field.
A further, advantageous embodiment provides for more than two radiation fields partially overlapping with one another to be used in order to obtain a conversion area in the light-sensitive layer.
In such a case, it is preferably provided for the radiation fields contributing to a single conversion area to be arranged so as to follow one another approximately at the same angular distance.
With respect to the partial superposition of radiation fields aligned at an angle or transversely to one another it is possible to superimpose the elongated radiation fields with one another with respective end areas located in the longitudinal direction.
It is, however, particularly advantageous when the elongated radiation fields are arranged such that at least one of the radiation fields is arranged so as to overlap with the other radiation field in a central area in order to generate a single conversion area.
It is even more advantageous when the radiation fields are arranged such that their central areas partially overlap one another.
Such an arrangement of the radiation fields has the advantage that with it the positioning accuracy of the two radiation fields relative to one another can be less and that, in addition, the most intensity is customarily available in the central areas of the radiation fields and so the superposition with central areas of the radiation fields also leads summarily to the highest obtainable intensity values and thus the intensity of the laser radiation can also, for example, be utilized in an optimum manner.
With respect to the time sequence, with which the at least two radiation fields are superimposed with one another, the most varied of solutions are conceivable.
One possibility, for example, provides for the control to control the laser radiation sources such that the radiation fields acting on a conversion area act on it one after the other with respect to time.
In such a case, the material of the light-sensitive layer has to be designed such that the first radiation field leads to a partial conversion of the material proceeding from the initial state and this partial conversion is maintained for such a time until the second radiation field acts and leads to the complete conversion into the converted state.
Another advantageous solution provides for the radiation fields to act on the conversion area in a manner overlapping at least with respect to time. In this case, it is sufficient for the material of the light-sensitive layer to keep the state reached due to the action of the first radiation field stored for such a time until the second radiation field acts on the material.
In a further advantageous case of the inventive solution it is provided for the control to control the laser radiation sources such that the radiation fields acting on a conversion area act on this simultaneously, wherein, in this case, the material of the light-sensitive layer experiences with respect to the intensity the effect of the sum of the two intensities and so the material need not be designed such that it stores a partial conversion with respect to time.
With respect to the design of the screen, it has been assumed thus far that this merely has an elongated screen aperture. This means that a laser radiation source controllable with respect to the intensity is to be associated with each screen aperture, wherein, in this case, a unit which is suitable for the control of the intensity and is supplied with a laser radiation of constant power also falls under the term laser radiation source, wherein the laser radiation of constant power can be made available to several such intensity-controlling units.
Therefore, at least one separate intensity control must be associated with each screen aperture in order to carry out the exposure when the screen aperture is located above the desired conversion area in the desired positioning.
It is, however, particularly advantageous when the screen has two screen apertures arranged so as to overlap and extending at an angle or transversely to one another and laser radiation is supplied to the screen in two directions of polarization, namely one direction of polarization, with which the first radiation field results, and one direction of polarization, with which a second radiation field extending at an angle or transversely to the first radiation field results.
The directions of polarization and the screen apertures preferably extend transversely, preferably approximately at right angles to one another in order to avoid any interaction of the polarized laser radiations.
In this case, only a single intensity control for both radiation fields is required since the overlapping area is already determined by the arrangement of the screen apertures in the same screen and thus an overlapping area of the radiation fields results which is already defined by the geometry of the screen apertures and so any positioning resources whatsoever for the arrangement of the second radiation field relative to the first radiation field and thus the positioning resources for an adequately precise overlapping can be dropped.
Even when an overlapping of more than two radiation fields is brought about for generating a conversion area, it is preferably provided for these to be generated by two screens each with two screen apertures crossing over one another in an overlapping manner.
In conjunction with the embodiment of an inventive lithography exposure device described thus far it has merely been assumed that the at least two radiation fields overlapping with one another for generating a conversion area can be generated with it.
However, in order to be able to produce sufficiently complex structures in a justifiably short time, it is preferably provided for the lithography exposure device to have a plurality of laser radiation sources for generating a plurality of laser radiations, with which a plurality of radiation fields can be generated which can be activated and deactivated by the control in accordance with the shape of the structure. As a result, several sections of the structure can preferably be produced in the same period of time within the scope of a single exposure movement, preferably even in a single exposure movement direction.
In this respect, it is preferably provided for the plurality of generatable radiation fields to have a first radiation field pattern consisting of first generatable radiation fields which are arranged in a defined manner relative to one another and the lateral extensions of which extend parallel to a first direction.
In this respect, the first direction can be aligned either parallel to the exposure movement direction or transversely to the exposure movement direction.
The first direction is preferably aligned transversely to the exposure movement direction.
An advantageous development of this embodiment provides for the first radiation field pattern, proceeding from a first radiation field serving as reference, to have first radiation fields arranged at different distances in a transverse direction extending at right angles to the exposure movement direction, for each first radiation field of the first radiation field pattern to have in the transverse direction a different distance from the first radiation field serving as reference than the remaining first radiation fields, for the distances of all the first radiation fields of the first radiation field pattern to form a series of distances, with which each distance is greater by one increment than another one of the distances and for the increment to be smaller than an extension of the first radiation fields in the transverse direction.
This solution has the advantage that only one movement of the optical focusing means relative to the light-sensitive layer in the direction of the exposure movement direction is controllable by the control for the production of at least one part of the structure and all the positionings of the radiation fields relative to one another for generating the structure can be brought about by activating the laser units generating the individual radiation fields.
Within the scope of the inventive solution it would be sufficient to work with the first radiation fields of the first radiation field pattern in an inventive manner, wherein only a partial superposition of radiation fields aligned in the same direction is possible.
In order to be able to also superimpose radiation field patterns aligned at an angle, in particular, transversely to one another with high precision it is preferably provided for the plurality of generatable radiation fields to have a second radiation field pattern consisting of second generatable radiation fields which are arranged in a defined manner relative to one another and the lateral extensions of which extend parallel to a second direction.
This second direction preferably extends at the angle or, in particular, transversely to the first direction.
In order to obtain the same high precision as with the first radiation fields, it is preferably provided for the second radiation field pattern, proceeding from a second radiation field serving as reference, to have second radiation fields arranged at different distances in a transverse direction extending at right angles to the exposure movement direction, for each second radiation field of the radiation field pattern to have in the transverse direction a different distance from the second radiation field serving as reference than the remaining second radiation fields and for the distances of all the second radiation fields of the second radiation field pattern to form a series of distances, with which each distance is greater by one increment than another one of the distances and for the increment to be smaller than an extension of the second radiation fields in the transverse direction.
In this respect, it is particularly favorable when the increment is at the most half the extension of the radiation fields in the transverse direction.
It is particularly favorable when the radiation field pattern comprises at least one series of first radiation fields arranged in a row, the fields having a distance from one another at right angles to the exposure movement direction which is smaller than their extension at right angles to the exposure movement direction.
As a result, it is possible to create a lithography exposure device, with which it is possible to generate the radiation fields with high precision within an area located at right angles to the exposure movement direction due to the extension of the series.
In this respect, it is preferably provided for the distance between the radiation fields of the series to be constant at right angles to the exposure movement direction.
In the simplest case, the radiation fields are arranged in the series in a row extending along a straight line.
A solution is particularly favorable, with which the radiation fields in the respective row have in series direction a distance from one another which is greater than their extension in series direction so that as a result of this distance a degree of freedom exists with respect to the arrangement of the radiation fields in the series direction.
In order to make it possible for the radiation fields to have in the transverse direction extending at right angles to the exposure movement direction as small a distance from one another as possible which is, where possible, smaller than the extension of the light spots in the transverse direction, it is preferably provided for the series direction to form with the exposure movement direction an angle of not equal to 90xc2x0, for example, smaller than 90xc2x0. As a result, the projection of the light spots arranged in the series onto the transverse direction extending at right angles to the exposure movement direction causes a reduction in the distance to the degree specified above.
In principle, semiconductor lasers, which generate laser radiation in the blue spectral range or in the close ultraviolet, may be used with the inventive device. As long as semiconductor lasers of this type do not, so far, have the price-to-power ratio required for commercial usage, it is preferably provided for the exposure unit to comprise frequency doublers connected after the semiconductor lasers. In this case, it is possible to use conventional semiconductor lasers operating in the red or infrared spectral range and to double the frequency.
In conjunction with the preceding explanations concerning the individual embodiments, it has not been explained in detail how the laser radiation is intended to be guided from the semiconductor lasers to the optical beam guidance means since the optical beam guidance means and the mounting device have to be movable relative to one another. For example, it would be conceivablexe2x80x94as already mentioned abovexe2x80x94to use the semiconductor laser arrangements or semiconductor laser arrays directly and, proceeding from this system, to image the individual laser beams onto the light-sensitive layer by means of the optical beam guidance means for generating the radiation field pattern so that the semiconductor lasers and the optical beam guidance means form a unit and this unit and the mounting device are movable relative to one another.
On account of the operating devices which entail considerable resources and are required for semiconductor laser units this is, however, in many cases possible only to a limited extent. For this reason, it is advantageously provided for the exposure unit to comprise light guides conducting the laser radiation to the optical beam guidance means. These light guides offer the possibility of bringing the laser radiation from semiconductor lasers arranged at a greater distance to the optical beam guidance means with as little loss as possible so that, in this case, the optical beam guidance means and the mounting device form the units movable relative to one another.
Monomode fibers are preferably used for light guides of this type and as semiconductor lasers those which operate in the single mode operation.
The light guides are preferably designed such that they have a first end, into which the laser radiation can be coupled, and a second end, from which the laser radiation exits, and that a collimating element is arranged to follow each second end, this element collimating the laser radiation exiting divergently from each individual second end of the light guides and forming a collimated radiation bundle therefrom.
Such a solution has the great advantage that it is possible to image the collimated radiation bundle onto the light-sensitive layer in an optimum manner and thus obtain as small a diameter of the resulting radiation field as possible, wherein, in this case, the second ends and the optical beam guidance means comprising the optical collimating means preferably form a unit and this unit and the mounting device are movable relative to one another.
With respect to the design of the optical beam guidance means, no further details have so far been given. One advantageous embodiment, for example, provides for the optical beam guidance means to comprise a telescopic device imaging on a reduced scale. With a telescopic device of this type it is possible to advantageously image the laser radiation, which is generated with the semiconductor lasers at great distances as a result of the technology and with respect to the size of the radiation fields to be generated, such that the distances between the radiation fields and the radiation spots themselves become smaller.
With such a telescopic device, reductions of more than a factor of 10 can be achieved in a simple manner.
In order, in particular, to be able to directly generate lithographic structures for the direct production of an integrated circuit, it is advantageously provided for the optical beam guidance means to comprise an optical microscope generating the radiation fields. Such an optical microscope offers a simple possibility of obtaining as great a reduction as possible in the distances between the individual radiation fields.
An optical microscope does, however, have the disadvantage that the extension of the radiation fields is severely dependent on the distance of the optical microscope from the layer to be exposed. For this reason, it is advantageously provided for the optical microscope to be arranged on a vertical positioning device and to be positionable by this during the exposure movement at a defined distance above the light-sensitive layer. Such a vertical positioning device thus creates the possibility of eliminating the disadvantages of such an optical microscope or keeping them as small as possible.
It is particularly expedient when a distance between an underside of the optical microscope facing the light-sensitive layer and the light-sensitive layer can be maintained by the vertical positioning device.
In this respect, it is preferably provided for the distance to be in the order of magnitude of a diameter of the individual radiation field on the light-sensitive layer.
With the optical microscope described thus far it is possible to obtain radiation fields which are limited in their diffraction and the extension of which is in the order of magnitude of the wavelength of the laser radiation.
However, in order to obtain as defined a size as possible of the individual light spots, in particular, in the range of the wavelength of the laser light used or smaller, it is preferably provided for the optical microscope to be provided with a near-field optical means defining the size of the radiation fields on the light-sensitive layer.
Such a near-field optical means has the great advantage that it opens up the possibility, on account of its closeness to the radiation fields generated on the light-sensitive layer, of determining the final size of the radiation fields on the light-sensitive layer to a great extent independent of the preceding beam guidance.
In this respect, the near-field optical means is preferably arranged directly on an underside of the microscope objective facing the light-sensitive layer so that the distance between the near-field optical means and the light-sensitive layer can be kept very small.
The near-field optical means may be designed in the most varied of ways.
One embodiment, for example, provides for the near-field optical means to define the radiation fields of the radiation field patterns by way of screen-like passage areas. In this case, screen-like passage areas can preferably be achieved by damping the optical microscope on its side facing the light-sensitive layer.
The inventive near-field optical means can be advantageously used, in particular, when this reduces the size of the radiation fields in at least one direction to values clearly below the wavelength of the laser radiation.
In this case, the vector of the electric field E of the laser radiation is expediently such that this lies parallel to the direction, in which the extension of the radiation fields is smaller than the wavelength.
Since the areal extension of the radiation field patterns cannot be optionally increased in size without the optical beam guidance means needing to be of a complicated construction, it is advantageously provided, in order to shorten the required exposure times, for the lithography exposure device to generate several radiation field patterns.
Each radiation field pattern has light spots arranged in a defined, geometrical pattern, wherein the several radiation field patterns can be optionally arranged relative to one another.
In principle, it is conceivable for the several radiation field patterns to be movable in different exposure movement directions.
To avoid crossover movements it is advantageous when the several radiation field patterns are movable parallel to a single exposure movement direction.
The several radiation field patterns can preferably be used during the same exposure procedure so that larger sections of the light-sensitive layer can be exposed during one exposure procedure.
In principle, it would be possible to generate the several radiation field patterns so as to be offset with respect to time. It is, however, more favorable to generate the several radiation field patterns essentially at the same time.
It is of advantage, in particular, in the case of radiation field patterns generated essentially at the same time when a separate optical microscope is provided for each radiation field pattern.
It is even better when a separate optical beam guidance means is provided for each radiation field pattern.
The several radiation field patterns could, in principle, be supplied from one set of semiconductor lasers, in particular, when the same exposed sections are intended to be generated with each radiation field pattern.
The possibilities of using an inventive lithography exposure device are, however, greater when a single set of semiconductor lasers is available for each radiation field pattern so that different exposed sections can be generated with the radiation field patterns.
A solution which is particularly simple to design provides several exposure units which operate independently for generating the several radiation field patterns.
The inventive object is accomplished according to the invention, in addition, with a lithography process for the production of structures extending in a surface area in a light-sensitive layer due to exposure thereof by means of a large number of successive exposure steps for generating a plurality of conversion areas in the light-sensitive layer which together result in the structures, wherein each exposure step serves to transfer the material forming the light-sensitive layer from an unexposed initial state into the converted end state within the conversion area by means of a radiation field and wherein the radiation field is generated in the light-sensitive layer by the focusing of laser radiation and additional limitation of the laser radiation in a lateral direction by means of a screen aperture elongated at right angles to the lateral direction with an effective extension in the lateral direction which is in the order of magnitude of the wavelength of the laser radiation or less, in that for the production of some of the conversion areas radiation fields are used with a distribution of energy which makes it necessary for the action of at least two radiation fields on the same conversion area in the light-sensitive layer to be required in order to transfer the material of the light-sensitive layer in this area into the end state.
The advantage of the inventive process is, in the same way as with the inventive lithography exposure device, to be seen in the fact that it is possible to obtain conversion areas with an extension which is smaller in at least one direction than the extension of the radiation fields used for this purpose.
In this respect, it is particularly favorable when the at least two radiation fields act on the light-sensitive layer in an overlapping manner and for an overlapping area thereof to cover the conversion area.
In this respect, the two, partially overlapping radiation fields can extend with their lateral directions parallel to one another.
Such a partial overlapping can, however, be achieved particularly advantageously when a first radiation field of the radiation fields acting on the same conversion area has the effective extension in a lateral direction along a first direction and that a second radiation field of the radiation fields acting on the same conversion area has an effective extension in a lateral direction which extends along a second direction extending at an angle to the first direction.
In this respect, it is possible to arrange the partially overlapping radiation fields such that they overlap with end areas. It is, however, particularly favorable when the radiation fields are superimposed such that the superposition is brought about in the central area of at least one of the radiation fields.
If more than two radiation fields are superimposed, it is preferably provided for these radiation fields to all be arranged at a different angle with respect to a selected radiation field.
In the case of several radiation fields, the radiation fields are preferably arranged such that radiation fields following one another in a direction of rotation are arranged relative to one another at approximately the same angular distance.
With a view to the action of the radiation fields with respect to time, no further details have so far been given. It would be conceivable, for example, in one solution for the radiation fields to act on the conversion area one after the other with respect to time, wherein, in this case, a precondition is that the material of the light-sensitive layer is such that the effect of the first radiation field is maintained, even though this has not yet resulted in a conversion of the material into the converted end state, and the action of the two radiation fields is added together, even if this occurs in succession with respect to time, so that altogether the conversion of the material of the light-sensitive layer into the converted state is achieved following the action of at least the second radiation field or also the additional radiation fields.
Furthermore, it would be conceivable for the radiation fields to act on the conversion area in a manner overlapping with respect to time so that the material of the light-sensitive layer stores the effect of the first radiation field for such a time until the second radiation field has acted.
A further, advantageous solution of the inventive lithography process provides for the radiation fields to act on the conversion area essentially simultaneously; this solution is of advantage, in particular, with a view to the time required for the inventive lithography process and in the case where the intensity of both radiation fields is intended, where possible, to take effect simultaneously.
Additional features and advantages of the inventive solution are the subject matter of the following description as well as the drawings illustrating several embodiments.